Anode for strapped magnetrons



March 1949. A. T. NORDSIECK ANODE FOR STRAPPED MAGNETRONS 2 Sheets-Sheet1 Filed May 8, 1946 INVENTOR.

ARNOLD T. NORDSIECK ATTORNEY March 1, 1949. A. T. NORDSIECK ANODE FORSTRAPPED MAGNETRONS" Filed May 8, 1946 2 Sheets-Sheet 2 INVENTOR.

ARNOLD T. NORDSIECK BY wm%. H4-

ATTORNEY Patented Mar. 1, 1949 2,463,416 ANODE FOR STRAPPED MAGNETBONSArnold 'li. Nordsieck, New York, N. Y., assignor to the United States bythe Secretary of War f America as represented Application May 8, 1946,Serial No. 668,135

8 Claims.

This invention relates to a built up anode for a strapped magnetron.

One of the objects of this invention is to provide an anode which may beaccurately constructed from readily fabricated parts.

Another object of this invention is to provide an anode which may beproduced without the use of turning or hobbing operations and whichavoids very small spacing between components.

Still another object is to provide an anode which has good modeseparation and large power output.

These and other objects will become apparent in the specification and inthe accompanying drawing in which:

Figure 1 is a sectional elevational view of the complete anode assemblyshown in conjunction with other components;

Figure 2 is a view of the anode assembly;

Figure 3 is an exploded view of the plates and washers utilized inconstructing the anode;

Figure 4 is a View of the built up anode with the strap assembly inposition.

As shown in Figure 1 the anode i0 is arranged in the usual fashionbetween the poles H of the magnetron. A cathode l2 contains a heatercoil, not shown, and extends into the anode and is provided. with acathode extension l3 through which the end of the coil projects and iswelded to a heater lead I4 in a manner well known in the art. Thecathode extension supports the cathode and acts in addition to conductaway the heat in the cathode. The anode is connected to an outputcircuit I6 through an impedance transformer 15.

As shown in Figure 2, the anode l0 comprises a series of washers 2| andplates 20 and 20a held together by suitable brazing or soldering at thejunctures. The bars or segments 22 and 22a connect together alternatingprojecting portions 25 in each layer and around the circumference. Thisconstruction permits good mode separation and results in other desirablecharacteristics such as high power output, good voltage-currentcharacteristics as well as ease of construction and feasibility ofreproduction of anodes having uniform characteristics.

As shown in Figure 3, plates 2!] and 200, are provided withsemi-circular cut-out portions 24 and have projecting substantiallybutt-ended portions 25 between said semi-circular cut-out portions.Plates 20 and 20a are identical and are merely rotated 180 with respectto each other. This results in a relative displacement of projectionsand indentations equal to an angular distance of one half the spacingbetween the semi-circular indentations, thus resulting in alternateplates so arranged that the projections of one plate over-lie theindentations of the other. For simplicity in manufacturing, the platesand the washers may be produced in mass production quantities bypunching in automatic presses. The material utilized is preferablyoxygen free high conductivity copper sheet. The Washers are preferablypunched from silver coated copper sheet. It should be noted that theplates as well as the washers are provided with a pair of holes 23diametrically opposite one another for purposes to be described later.

The right hand portion of Figure 3 shows the completed bar assemblyprior to insertion into the anode stack. This assembly is made of coppertubing which has previously been. coated or pated with silver. By meansof a simple milling operation, slots are milled into the tube leavingstrips of metal 22 and 22a attached at their ends to the ends 26 of thetube.

In Figure 4, the anode assembly is shown to consist of a stack ofalternate washers and plates with alternate plates rotated in. themanner shown in Figure 3 and described in connection therewith. Holes 23facilitate this particular assembly arrangement by receiving closefitting metal pins, not illustrated in the drawing, to insure accuratealignment of portions 25. These pins may be made of silver coated copperin which case they will remain in the assembly after brazing. If desiredthe pins may be incorporated in the jig assembly described below. Inthis modiiication the pins may be made of stainless steel to facilitatetheir removal after brazing. The strap assembly is inserted so as toprovide contact between alternate anode projections bothcircumferentially and by alternate plates. Thus bars 22 connectprojections 25 on plates 23 while straps 22a connect projections 25 onplates 20a, see Fig. 2. The entire assembly as shown in Fig ure 4 isclamped tightly in a suitable jig means and is placed in a furnace wherethe silver coating of the strap assembly and of the washers fuses andresults in a substantially electrically homogeneous bond between thevarious parts of the anode assembly. In the case where copper pins areused for aligning the anode members the jig may comprise a simpleparallel vise. The completed anode is then turned on a lathe to cut offthe surplus tubing at ends 26 of the bar assembly and the resultantanode shown in Figure 2 is complete and ready for subsequent operationsof assembly into a tube.

The geometry of the tube is very favorable for producing a good modeseparation and in some ways may be likened to an interdigital anode inwhich a multiple inter-connected interdigital assembly has beenutilized. From another point of view it might be considered that theentire anode produced by this invention, with the exception of thelongitudinal bars 22 and 22a, consists of strapping whose geometry hasbeen arranged to form an anode body, the tube inductance being suppliedby quarter Wave sections joining segments 22 and 22a rather than bycavity resonators arranged in a circle as in conventional anodes.

An electrical advantage of this type of anode is that the anode heightmay be increased, in order to increase the power capacity, to values ofthe order of one free space wave length without changing the electricalbehavior, by merely increasing the number of plates 20 and 20a andwashers 2|. That is to say, each annular cavity created by a washer 2i,together with the coplanar parts of the bars and the cathode,constitutes an independent magnetron oscillator and any number of theseup to the limit stated above may be operated in parallel, the bars 22and 2211 serving to hold them electrically in phase. In the figures fivesuch sections are shown in parallel. In this respect the anode heredisclosed is like the rising sun anode and differs from the conventionalstrapped anode, which latter is limited to heights of about one-thirdfree space wave length.

The theory behind the operation of a tube of this type is as follows:Consider a pill box shaped resonator oscillating in its fundamentalmode. Such a resonator is desirable for a magnetron oscillator becauseits additional modes are quite far removed on the high frequency side.In such a simple form, however, the resonator is not suitable formagnetron operation because the radio frequency electrical field isdirected axially rather than circumferentially and is independent ofangle rather than reversing periodically with angle. If scalloped holeslike those in parts 20 and 20a are cut in the top and bottom of the pillbox and bars like 22 and 22a are attached so that alternate bars areconnected to the top and bottom respectively the required reorientationof the electric field is accomplished without losing the above mentionedadvantages of the pill box resonator. Each of the five sections shownand referred to above may be though of as such a redesigned pill box.

An anode constructed according to these principles is very efiicient atfrequencies in the range of 20,000 mc./sec. to 30,000 mc./sec., and hasa good mode separation. Its output in this frequency range has amountedto over 20 kilowatts, the limitation being due to cathode constructionrather than to any characteristics of the anode itself.

While I have shown a single embodiment of my invention, it is obviousthat other cavity and strapping configurations and arrangements may beutilized in accordance with these teachings and I therefore do notintend my invention to be limited except within the scope and extent ofthe appended claims:

I claim:

1. A strapped magnetron anode comprising alternate apertured discshaving their inner surfaces serrated and forming projections, washersbetween said discs for producing a spacing between the latter, and barsconnecting only alternate projections within the apertured discs.

2. A method for producing a magnetron anod comprising stacking alternateapertured dis members and washers, inserting a cylindricz unitarysegment assembly comprising a pluralit of bars connected to each otherat their end: heating said stack and segment assembly to ob tain fusionand bonding between the parts, an removing portions of the segmentassembly t provide bar members connected to alternate dis members.

3. A magnetron anode comprising alternatl apertured discs and Washers inelectrically con ducting relation forming quarter wave sections and barsconnecting only alternate discs.

4. A magnetron anode comprising a pluralit: of spaced, electricallyconnected, apertured discs said discs being provided with spaced,internally extending projections, and bars connecting only alternateprojections in alternate discs.

5. A magnetron anode comprising a plurality of stacked apertured discsand washers, and bars connecting only alternate discs forming aninterconnected interdigital segment assembly.

6. A method for producing a magnetron anode comprising forming a stackof axially aligned apertured disc members separated by axially alignedwashers having a fusible outer layer, inserting a unitary bar assemblyhaving a, fusible outer layer within the apertured disc members, heatingsaid disc, washer and bar assembly to obtain fusion of the fusiblelayers and bonding between the elements, and removing portions of thebar assembly to provide a, plurality of independent bar members.

7. A magnetron anode comprising a series of stacked apertured discsseparated by washers, the outer diameter of said discs and said washersbeing equal but the inner diameter of said washers being larger than theinner diameter of said aperture discs, the apertures in said discs beingcentrally-located, circular apertures with scallops radially disposedalong the circumference of each aperture, said scallops forming a,plurality of radially disposed teeth, said scallops and said teethhaving equal dimensions and being equally spaced around thecircumference of said aperture, the teeth of one disc being in staggeredrelationship with respect to the teeth of adjacent discs, whereby theradial axis of one tooth of one disc and the radial axis of a scallop inadjacent disc are in a single plane, and a plurality of barsinterconnect ing the inner ends of said teeth of alternate discs, thevolume between said adjacent discs defining a resonant cavity of thepill-box type in its fundamental mode, and the bars connected toalternate discs assume alternately positive and negative potentialsaround the circumference of said anode.

8. A magnetron anode as defined in claim 7 in which the axial dimensionof said anode is of the order of one free space wave length, said wavebeing the operating wave of said anode.

ARNOLD T. NORDSIECK.

REFERENCES CITED The following references are file of this patent:

UNITED STATES PATENTS of record in the Disclaimer 2,463,416.-A1 rmld T.N ordsieek, New York, N. Y. ANODE r01: STRAPPED MAG- NETRONS. Patentdated Mar. 1, 1949. Disclaimer filed Oct. 3, 1951, by the assignee, Um'ted States of America, as represented by the Secretwy 0 f the Army.Hereby enters this disclaimer to aims 1, 3, 4, and 5 of said patent.

[Oficial Gazette October 30, 1951.]

